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History

History. Television Cameras In the 1920s, American engineer, Philo Taylor Farnsworth devised the television camera, an image dissector, which converted the image captured into an electrical signal. http://inventors.about.com/library/inventors/blvideo.htm

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History

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  1. History • Television CamerasIn the 1920s, American engineer, Philo Taylor Farnsworthdevised the television camera, an image dissector, which converted the image captured into an electrical signal. http://inventors.about.com/library/inventors/blvideo.htm • Charles P. GinsburgCharles Ginsburg led the research team at Ampex Corporation in developing the first practical videotape recorder (VTR). In 1951, the first video tape recorder (VTR) captured live images from television cameras by converting the information into electrical impulses and saving the information onto magnetic tape. Ampex sold the first VTR for $50,000 in 1956.The first VCassetteR or VCR were sold by Sony in 1971. http://inventors.about.com/library/inventors/blvideo.htm

  2. History continued • first cameras used tubes to capture the light fed into it via a camera lens • Solid state devices (like an integrated circuit) now fit the bill

  3. Basics - Video communications • The sensing device in a video camera is analog using light as the input – Base band video • Video signals are very complex signal electronically • changes with light intensity, color, and motion • Audio is handled differently in the base band state

  4. Video signal characteristics • Standards for different venues, NTSC, PAL, SECAM • Now HD, SD, 720p, 1080i, 1080p • Timing for H and V • Lighting • Motion • Color content • Color reference • Demo – waveform monitor to camera to screen

  5. Vidicon Tubes used in video cameras Used in Broadcast Surveillance Recording studios

  6. Current technology used for image pickup CCD or: Charged Coupled Device

  7. Colors used in Video Why Red, Green, and Blue? The normal human eye has three kinds of color receptors that are sensitive primarily to red light, green light, and blue light respectively. While, for example, yellow light stimulates both the red and green receptors (and minimally if at all the blue receptors) the same stimuli are accomplished by representing yellow portions of a video picture using tiny red and green spots.

  8. How color is recorded electronically

  9. WAVEFORM MONITOR DISPLAY Each Point represented a part of the color video information

  10. Example of a video clip

  11. Broadcast • Base band video can run over cable a short distance before the signal quality starts to deteriorate • High Frequencies start to “roll off” (level drops and resolution decreases, sharp edges become fuzzy) • Signal level drops – video becomes dimmer • Only one signal over any given cable • Frequencies used do not lend themselves to being transmitted over the air waves • Frequency spectrum chart

  12. Broadcast Video – continuedThe electromagnetic spectrum • Modulation basics • Different frequencies for different channels • http://en.wikipedia.org/wiki/Electromagnetic_spectrum • Transmitters and antennas • Transmitters up converts the frequencies – modulation • Antennas transfers the electrical energy to electromagnetic energy and vice versa

  13. CATV Rather than open air broadcast the signal is sent over cable. Current systems use a combination of Fiber and coax

  14. Video signals over coax • Limited runs based on quality and size of coax • Typical cables used in video transport • RG 59 very common, my use typically were runs of 100’ or less • Newer systems are using RG 6 - + 100’ runs • Studio used higher quality coax cable with quad shield and larger center conductors • Need to transport the signal over longer distances • Frequencies used in base band video didn’t lend themselves to long runs over coax or for transmission purposes

  15. Modulation • A modulator is a device that performs a conversion of the base band frequencies up-converted to a specific channel (range of frequencies set aside for a specific use) and a device that performs the inverse operation of modulation is known as a demodulator . • What is the demodulator called in a TV? • A device that can do both operations is a modem (a contraction of the two terms).

  16. Analog • The CATV systems • TV channels in house didn’t necessarily line up with Broadcast channels. • Demodulators, modulators were used to move the program to a new channel • Early systems maintain channel separation to avoid interference problems

  17. CH 2 RF distribution System Demod Mod. Combiner Combiner TAP CH 5 Demod Mod. CH 11 Demod Mod. Splitter/ CH 26 Demod Mod. Amp CH 32 Demod Mod. CH 38 Demod Mod.

  18. Digital • "DTV" IS COMING(AND SOONER THAN YOU THINK!) • FCC Consumer FactsOn February 17, 2009, federal law requires that all full-power television broadcast stations stop broadcasting in analog format and broadcast only in digital format. Here’s what these requirements will mean for you and your television viewing.

  19. Digital TV • Why Are Broadcast TV Stations Switching to All-Digital? • Congress mandated the conversion to all-digital television broadcasting, also known as the digital television (DTV) transition, because digital is a more efficient transmission technology that allows broadcast stations to provide improved picture and sound quality, as well as provide more programming options for consumers through multiple broadcast streams (multicasting). In addition, all-digital broadcasting will free up many frequencies to be used for public safety, such as police, fire, and emergency rescue, and for the provision of advanced commercial wireless services for consumers.

  20. FCC web site :http://www.fcc.gov/cgb/consumerfacts/digitaltv.html • How Do I Receive Digital Broadcasts If I Don’t Subscribe To Cable Or Satellite? • If you receive only free over-the-air television programming, the type of TV you own, either a digital TV or an analog TV, is very important. Consumers who receive only free over-the-air television may view digital programming through a TV set with a built-in digital tuner (integrated DTV) or a digital-ready monitor with a separate digital tuner set-top box. (Both of these digital television types are referred to as a DTV). The only additional equipment required to view over-the-air digital programming with a DTV is a regular antenna, either on your roof or a smaller version on your TV such as “rabbit ears.” • If you have an analog television, you will have to purchase a digital-to-analog set-top converter box to attach to your TV set to be able to view over-the-air digital programming (see “What About My Analog TV?” below).

  21. Digital TV or DTV • The Analog signal is converted into a digital form and a method for encoding the digital information is set. The digital signal is then transmitted over the air waves (satellite or local television station) or through a cable system. • Standard Definition SDTV will be at the same quality level of current analog channels. 3x4 or 16x9 • Enhanced Definition TV EDTV will be a higher quality comparable to DVD players. • High Definition TV HDTV will provide an even higher quality signal. 720P and 1080I

  22. IPTV • IPTV (Internet Protocol Television) is basically the delivery of the digital TV signals over an internet based system. In other words, the digital video signal is delivered via a computer network rather than a broadcast signal or over a CATV system. • “The commercial bundling of IPTV, VoIP and Internet access is referred to as "Triple Play" service (adding mobility is called "Quadruple Play"). IPTV is typically supplied by a service provider using a closed network infrastructure. “ • In businesses, IPTV may be used to deliver television content over the businesses local area network.

  23. Discuss cable types used in video

  24. Lab • Demo of a video signal, scope results • Discuss RF modulation • Discuss RF radiation versus transmission down a cable • Cable construction and testing • Reading assignment for next week • Pages: 65 through 85

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